Process of concentrating nitric and sulfuric acid



A. C. BOHRE, DECD.

K. C. BOHRE. EXECUTRIX.

PROCESS 0F CONCENTHATING mmc AND suLFuRlc ACID.

APPLICATIUN FILED JULY 28, |919. 1,338,418. Patented Apr. 27, 1920.

UNITED sTATEs PATENT oiriucE.l

NORWAY, BY NORWAY.

ANTON CHRISTIAN BOHBE, D'ECEASED, LATE 0F CHRISTIANIA, KATHARINA CHARLOTTE BOI-IRE, EXECUTRIX, OF BERGEN,

PROCESS 0F CONCENTRATING NITBIC AND SULFURIC ACID.

1,338,418, specification of Leners Patent. Patented Apr. 27, 1920.

' Application illed July 2B, 1919. Serial No. 313,849.

To all whom t ma?L concern: A gas is suitably passed in such quantity Be it known t at I, KATHARINA CHAR- through the liquid, that the water hereby evaporated absorbs a uantity of heat corresponding to that evo ved in the condensa-l tion apparatus. The liquidhereby recooled can then be returned to the condensation apparatus. In the course of this cooling process a concentration of the dilute acid Lo'i'rE Bouma, a subject of the King of Norway, of Bergen, Norway, executrix of the estate of ANTON CHwiiis'riAN BonRE, late of Christiania, Norway, do declare that he, the said ANTON Hnis'riAN BoHiiE, has invented certain new and useful Im rovements in Processes of Concentrating itric and condensed in the condensation apparatus Sulfuric Acid; and I do further declare the also takes place. following to be a full, clear, and exact de- The recess may for instance be carried scription of the invention, such as will en into e ect in the following manner, referable others skilled in the art to which it ence beingl had tothe accompan ing drawap ertains to make and use the same. ing, in w ich a concentration Agiant is dahis invention relates to the concentrarammatically illustrated. tower A tion of nitric and sulfuric acid by the action lled with acid resisting material, is charged at the top at f with dilute acid (viz. nitric acid or sulfuric acid containing some nitric acid). Hot nitrous gases are introduced at a. The gases in passing through the tower take up water vapor and also some acid vapors from the acid. At the bottom the acid is discharged at g as concentrated acid', (viz: nitric acid of Yabout 65 per cent. or sulfuric acid of about 95 per cent). The gases char ed with vapors of water and of acid are ed throu h the ipe b to the bottom of a tower B c arged with dilute nitric acid. This acid is supplied to the top of the tower at h at a temperature 'o bout 20-30 C In this of hot nitrous gases.

As known several attempts have been made to effect the concentration of dilute nitric acid and of sulfuric acid containing soine nitric acid by means of hot nitrous gases. The attempts hitherto made to carry this process into effect on a commercial scale have not however met with success because of the diiiicultes involved by the ac-f tion of the'treated substances upon the materials as well as by the large dimensions necessary to obtain the requiredy cooling surface;`

According to the present invention it is now possible to eifect the concentration of dilute acids by the action of hot nitrous ases in such a manner as to avoid the diiculties hitherto met with. -This is attained by a rocess, which consists in passing the hot nitrous gases in direct contact wit the acid to be concentrated, condensin the re# sulting vapors by passing the mixture of ases and vapors in contact with a cooling liquid, and thereupon lowerin the temperature of the so used cooling iquid so as to prepare it for repeated use as a cooling li uid by passing a current of aA gas throng the same. In this process the concentration of the acid, the condensation of the resulting vapors and the recooling of the liquid employed to effect the condensatioi`take place in separate scrubbers or irligation towers, the gases and liquids being preferably passed in counter current to each other.

a tower practically the entire acid vapor yleaving the tower A is condensed and also so `much of the water, that the escaping gases are only saturated with waterwapor at a temperature of 20-30. The nitrous ggses leaving this tower at c can now safely introduced into the absorption system for the absorption of the nitrogen oxids contained therein. y

The heat of condensation evolved in the tower B, which corresponds to the quantity of heat, which the gases/have given oi in the tower A, raises the temperature of the cooling liquid to for instance -60 (depending of course upon the quantity o liquid circulating through the tower). This hot cooling liquid is now led pipe 'tol a tion as the tower is blown a current The condensation ap aratus is then gases for instance the gases charged with water or ute acid, which sorption system for the nitrous gases( x acts as a cooling liquid. To recool this ployed in the manufacture of nitro n comcondensation liquid after use air or other pounds by the combustion of air nitrogen?,

This gas enters at al and escapes at e. In many instances the last acid tower in the absorption system can be used with advantage as the tower C. In contact with the hot liquid the air or the ases are heated and take up moisture, where y heat is again absorbed. The current of gas is so controlled that in the tower C so much water is evaporated that the heat therebyT absorbed corresponds to the heat evolved in B. The temperature of the liruid fiowing through the tower C is thereby owered to such aegree that the liquid can again be used in the tower B. In order to maintain the liquid circulating through B and C at a constant temperaturea proportion of the li uid is removed, a corresponding quantity o water or of a-more Vdilute acid being at the same time supplied. The gases escaping from C contain only water vapor and can be let out directly at into the open air.

The described method has the advantage of allowing the concentration to be eifected in a very simple and reliable apparatus, in which a very good concentration and cooling action is obtained owing to the direct contact of the liquids to be concentrated and condensed with the gases.

Claims: y I l 1. Process for the concentration of n1tr1c or sulfuric acid comprising the steps of passin hot nitrous gases in contact with the acid to be concentrated, condensing the resulting vapors by passing the mixture of gases and vapors 1n contact with a cooling liquid, and thereupon lowering the temperature of the so used cooling liquid by passing a current of gas through the same so as to prepare it for furtheruse as a cooling li uid.

2. Process as dened in claim 1 in w ich the residual gas-obtained when the nitrous' Kirnlm'iu CHARLOTTE Bonini, Emecutr of the estate of Anton Christian Bolwe, deceased.

Witnesses ODD BJAcoBsEY, J oHN` KAMMRR.

Correction In Letters Patent No. 1,338,418.

It is hereby certified that Letters Patent No; 1,338,418, granted April 27', 1920, upon the application 'of' Katharina Charlotte Bohre: of Bergen, Norway, as executrix of Anton Christian Bohre, deoesed, vfox' an improvement in Proees-es of onoentrating Nitric and Sulfurio'Aeid, were erroneously issued te said Kotherina Charlotte Bohre, executrx, as owner of seid invention, whereas seid Let.- ters Patent should have been issued to Norsk Hydro-Elektrek Kyaelstofakte'eselakab, of Uheania, Norway, es assignee of the entire ntereet in said invention os shown by the record of asignmente in this OHc; dnd that'the said Lettera lli'rntent should be r'ead with this cogrection therein that the aime may oonform' the record of the in the'Patnt. O Hce. Signed andftenled this 58th day of September, A. D.,; 1920. Y 4 M'. H; coxuLsToz, A

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